Thought I'd share my experiences so far after switching from the OEM 20" Goodyear Forteras to a set of 275/55-20 Toyo Open Country AT IIs. I realize there's more tread and these tires are about 1.5 inches taller, but I was surprised after taking my first road trip and seeing about a 4 mpg decrease. I'm not sure I would have went with these tires/size had I known this. Mpgs went from around 24 on the interstate @ 60-70 mph to 20. Ugh.

I think if you are using your jeeps on-board MPG display it will not be accurate. Because of the larger overall diameter you will actually be traveling farther than it thinks per tank, about 5%. So while your jeep might think it is traveling 400 miles after using 20 gallons of fuel, its was actually traveling 420 miles, it just doesn't know any better because the speedometer would be off due to the different tire size.

Try calculating manually, and adjust miles for your tire size. This is common when upsizing, or switching from highway all-season to an aggressive A/T tire. You did both. You also take a hit with winter gas. 4 MPG is quite a bit. There are too many factors in mpg. You can't make an assumption based on 1 trip or 1 tank. You have to average over time. Wind, temp, terrain, etc. all make a significant difference in mpg. Report back after 3 months, or back in Spring time -- when summer gas hits. Your speedo and odometer are both reporting lower than actual now.

I think if you are using your jeeps on-board MPG display it will not be accurate. Because of the larger overall diameter you will actually be traveling farther than it thinks per tank, about 5%. So while your jeep might think it is traveling 400 miles after using 20 gallons of fuel, its was actually traveling 420 miles, it just doesn't know any better because the speedometer would be off due to the different tire size.

does that sound correct?

I got out my calculator and figured that at 70 mph for the 6-hr trip I took, the larger tire size on my odometer cheated me out of almost exactly 1 mpg as calculated by my trip computer. Thanks for the heads up. I didn't take that into consideration.

Quote:

Originally Posted by WK2OverlandII

Can you post some Pics? I would like to see what they look like...also do you have any rubbing when turning?

I don't have any right now, but I can post them when I get a chance. No rubbing whatsoever, even in aero mode.

After the speedo correction, 1-3mpg decrease is normal, for switching to a taller, haevier, and more aggressive tread tire. I lost 2mpg going to a 31.5" Nitto AT tire. The tire itself is 14lbs heavier than oem.

I have Wrangler Rubicon tires on mine now but I basically instantly hated it when I put them on. Way too loud, handle like crap, bumpy, etc. I loved these tired on my Rubicon but they ruin the GC ride.

This is the reason I stayed with OEM 17" Forteras when I re-upped at 50k on my 2010. Performance on the Forteras was fine--including packed snow and ice--and I couldn't take a chance the LTX's would bring a mileage downgrade.

Here's the math, and it ain't pretty:

20k miles per year at 20 mpg vs 17mpg= $600 penalty EACH YEAR at $3.40 per gallon. No thanks!!

This is the reason I stayed with OEM 17" Forteras when I re-upped at 50k on my 2010. Performance on the Forteras was fine--including packed snow and ice--and I couldn't take a chance the LTX's would bring a mileage downgrade.

Here's the math, and it ain't pretty:

20k miles per year at 20 mpg vs 17mpg= $600 penalty EACH YEAR at $3.40 per gallon. No thanks!!

Way to make everything real john, gawd!

Seriously though, the numbers really speak for themselves once you put it all together. I also decided to hold off on getting some new tires for the time being until I really need them. After doing tons of research, I basically talked myself out of them for the mileage hit and just how unnecessary they are for the new car right now. Always tons of things to take into consideration.